Hydraulic control valve question

[Hacksawhero123 351]

I need the wisdom from the hydraulic wizards. In my collecting of parts, I have two different styles of "inlet" blocks. This is the block that is marked "in" and gets pressure from the charge pump. The red block in the photo is the one that is different from the factory block on my 1975 c160. Am I correct in assuming that the bolt/spring assembly is a pressure relief valve?  Could this be a power beyond port?  Thanks Fellas. 

Mark. 

Edited January 21, 2017 by Hacksawhero123

[gwest_ca-(File Mod) 11,045]

I can't answer your question and there is limited info available for these units.

Garry

[Hacksawhero123 351]

Thanks Gwest. I forgot that I had downloaded that before. Getting old I guess. I would like to find a valve with the float detent though. Thanks again. 

Mark. 

[R. L. Addison 299]

I think that is to relieve pressure with temp change,(sitting in the sun or such). As the oil gets hot, it expands enough to put unbelievable pressures in the system, and in cases of larger volumes heating, has been known to blow hoses etc. It looks to me like a safety feature.  I think the power beyond would have to come through the return line, as these valves would have to be open centered as charge pump could not supply oil to closed loop to make up for valve plate and other leakage in the pump/motor unit.

[Dennys502 244]

The pressure relief valve is used to control line pressure - depending on what psi the system is designed for. Anything over the pressure its set at gets dumped back to tank.

[cleat 5,998]

I have played with the hydraulics on my diesel tractor.

 

That is a pressure relief valve.

 

My new loader valve has a power beyond outlet.

However, my old hydraulic valve also had hydraulics downstream for rear remotes and 3 point.

The old one just used the outlet from the valve feeding the inlet to the next valve in line.

 

My new loader valve with the power beyond uses the power beyond port to feed downstream valves and also has it's own return to tank fitting.

 

That means I had to add another line back to the tank. Seems to work exactly the same so I am unsure what the benefit really is.

 

One word of caution. When replacing a hydraulic valve you should hook up a gauge and make sure the relief valve is working and set to proper pressure.

 

Cleat

 

[R. L. Addison 299]

The hydraulic pressure is set by shims in the pump valve body which controls a cone, to determine system pressure. The pressure adjustment on the spool valve bank can also control system pressure if it is set to a lower pressure than the one in the valve body, as the oil will take the path of least resistance. 

 

The reason I would come out of the return line to any other hydraulic function is there would be no "T"'s needed, and the charge pump has a very limited capacity and more than one action at a time will be slow due to the small volume of this pump. The exception to return line might be power steering, might put it in line before lift valves. Hope you can follow this. If not, QUESTION!

[Hacksawhero123 351]

Thanks Fellas. I was pretty certain that it was a relief valve. That block is the oddball in my spare parts bin. The factory inlet block doesn't have the relief valve, just curious why this block has it. If anyone has a spool valve with the float detent they want to turn into cash, please let me know. 

Mark. 

Edited January 21, 2017 by Hacksawhero123